Semiconductor module and method of manufacturing semiconductor module

ABSTRACT

An object of the invention is to manufacture a semiconductor module small. A metal wire ( 212 ) connecting a control electrode ( 101 ) and a control terminal ( 21 ) rises to form a first angle (θ 1 ) from the control electrode ( 101 ) toward a first conductive portion ( 202 ), gradually goes in substantially parallel to the first conductive portion ( 202 ) as the metal wire approaches the first conductive portion ( 202 ), and is connected to the control terminal ( 21 ) to form a second angle (θ 2 ) smaller than the first angle (θ 1 ).

TECHNICAL FIELD

The present invention relates to a semiconductor module and a method ofmanufacturing the semiconductor module.

BACKGROUND ART

As a related art of a semiconductor module used in a power conversiondevice, PTL 1 discloses “Provided is a semiconductor device which canefficiently radiate heat from main surfaces in the vertical direction ofthe semiconductor device with a semiconductor element mounted thereon”and “In a semiconductor device 4, a metal foil 10 ac of an insulatingsubstrate 10A is disposed up to the vicinity of the end of an insulatingplate 10 aa (Portion C in the drawing). An insulating plate 10 ga isprovided separately, a control terminal 10 g is connected to the uppersurface side of the insulating plate 10 ga, and a metal foil 10 gb isconnected to the lower surface side of the insulating plate 10 ga” inthe abstract.

CITATION LIST Patent Literature

-   PTL 1: JP 2014-60410 A

SUMMARY OF INVENTION Technical Problem

In recent years, a potential difference between the members in thesemiconductor module becomes large as the semiconductor module isincreased in voltage. When a plurality of members different in potentialfrom each other are disposed, a dimension is determined in considerationof a variation caused at the time of manufacturing while securing aninsulation distance as long as a dielectric breakdown can be prevented.Therefore, there is a problem in increasing the size of thesemiconductor module. The invention has been made in view of the aboveproblems, and an object thereof is to provide a semiconductor module anda method of manufacturing the semiconductor module which can bemanufactured small.

Solution to Problem

According to the invention to solve the above problem, a metal wireconnecting a control electrode and a control terminal rises to form afirst angle from the control electrode toward a first conductiveportion, gradually goes in substantially parallel to the firstconductive portion as the metal wire approaches the first conductiveportion, and is connected to the control terminal to form a second anglesmaller than the first angle.

Advantageous Effects of Invention

According to this invention, it is possible to manufacture asemiconductor module small.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a power module according to anembodiment of the invention.

FIG. 2 is a circuit diagram of the power module.

FIG. 3 is a perspective view of the power module from which a sealingportion is removed.

FIG. 4 is a perspective view of an IGBT chip.

FIG. 5 is a cross-sectional view taken along a line A-A′ in FIG. 3.

FIG. 6 is an exploded perspective view of the power module in a statewhere the sealing portion is removed.

FIG. 7 is a diagram illustrating a manufacturing process of the powermodule.

FIG. 8 is a diagram illustrating another manufacturing process of thepower module.

FIG. 9 is a diagram illustrating another manufacturing process of thepower module.

FIG. 10 is a diagram corresponding to a cross-sectional view taken alonga line A-A′ of a power module according to a comparative example.

FIG. 11 is a diagram illustrating a configuration of a power module in amodification of the embodiment.

DESCRIPTION OF EMBODIMENTS Configuration of Embodiment <OverallConfiguration>

Next, a configuration of a power module according to an embodiment ofthe invention will be described. FIG. 1 is a perspective view of a powermodule 901 according to this embodiment. The power module 901 has asubstantially rectangular plate shape, and provided with heat radiatingportions 402 and 403 of a rectangular thin plate shape in two surfaceswhich are disposed in parallel to face each other. The surfaces on theoutside of the heat radiating portions 402 and 403 (exposed surface) arecalled heat radiating surfaces 42 and 43. A plurality of plate terminals(that is, an emitter terminal 22, a collector terminal 23, a pair ofgate terminals 21, and a pair of sense emitter terminals 25) protrudefrom one of the side surfaces of the power module 901, interposedbetween the heat radiating surfaces 42 and 43. A sealing agent fillsportions except the heat radiating surfaces 42 and 43 and the respectiveterminals so as to form a sealing portion 11.

Next, a circuit configuration of the power module 901 is illustrated inFIG. 2. The power module 901 includes a pair of insulated gate bipolartransistor (IGBT) chips 100 equipped with the sense emitter, a collectorcircuit portion 203 which mutually connects collector electrodes of theIGBT chips 100, an emitter circuit portion 202 which mutually connectsemitter electrodes of the IGBT chips 100, and a pair of freewheel diodechips 110 which are connected to the emitter circuit portion 202 and thecollector circuit portion 203.

The emitter circuit portion 202 is connected to the emitter terminal 22,and the collector circuit portion 203 is connected to the collectorterminal 23. In addition, a gate electrode and a sense emitter electrodeof each of the pair of IGBT chips 100 are connected to the gate terminal21 and the sense emitter terminal 25 respectively. As is well known, theIGBT chip 100 controls the ON/OFF state of the terminals 22 and 23 by avoltage applied to the gate terminal 21.

Next, a perspective view of the power module 901 in a state where thesealing portion 11 in FIG. 1 is removed is illustrated in FIG. 3. Theheat radiating portion 402 illustrated in FIG. 1 occupies a part of aceramic substrate 12 on the emitter electrode side. In other words, theceramic substrate 12 includes a ceramic insulating layer 302 of therectangular plate shape, and the heat radiating portion 402 of therectangular plate shape which is formed in the outer surface andslightly smaller than the ceramic insulating layer 302. In addition, aceramic substrate 13 on the collector electrode side is disposed in therear surface of the power module 901 to face the ceramic substrate 12 onthe emitter electrode side. Then, the pair of IGBT chips 100 and thepair of diode chips 110 are interposed between the ceramic substrates 12and 13. The gate terminal 21 and the sense emitter terminal 25 areconnected to the IGBT chip 100 through metal wires 212 and 252. Inaddition, the emitter terminal 22 and the collector terminal 23 areconnected to places facing the diode chips 110.

Next, a perspective view of the IGBT chip 100 is illustrated in FIG. 4.The IGBT chip 100 is formed almost in the rectangular plate shape, andincludes an emitter electrode 102 which is formed as a main electrode inthe upper surface and a collector electrode 103 which is formed as amain electrode in the lower surface. In addition, a gate electrode 101and a sense emitter electrode 104 are formed as control electrodes inalignment with the emitter electrode 102. The shape of the diode chip110 is formed in the rectangular plate shape having almost the samedimension as that of the IGBT chip 100 while not illustrated in thedrawing, and includes an anode electrode in the upper surface (aposition corresponding to the emitter electrode 102) and a cathodeelectrode in the lower surface.

Next, a cross section taken along a line A-A′ in FIG. 3 is illustratedin FIG. 5. In FIG. 5, the ceramic substrate 13 on the collectorelectrode side includes a ceramic insulating layer 303, the heatradiating portion 403 which is bonded to the outer surface, and thecollector circuit portion 203 which is bonded to the inner surface.Then, the collector electrode 103 of the IGBT chip 100 is electricallybonded to the collector circuit portion 203 through a metal bondingportion 803. In addition, the collector circuit portion 203 and the heatradiating portion 403 are electrically insulated by interposing theceramic insulating layer 303 therebetween.

In addition, the ceramic substrate 12 on the emitter electrode sideincludes the ceramic insulating layer 302, the heat radiating portion402 which is bonded to the outer surface, and the emitter circuitportion 202 which is bonded to the inner surface. A conductor block 202Awhich is a metal block of a cuboid shape is inserted between the emitterelectrode 102 and the emitter circuit portion 202 of the IGBT chip 100.The conductor block 202A is bonded to the emitter circuit portion 202and the emitter electrode 102 through metal bonding portions 801 and802, so that the emitter electrode 102 and the emitter circuit portion202 are electrically connected. In addition, the emitter circuit portion202 and the heat radiating portion 402 are electrically insulated byinterposing the ceramic insulating layer 302 therebetween.

Next, an exploded perspective view of the power module 901 in a statewhere the sealing portion 11 is removed is illustrated in FIG. 6. Inthis case, the state of the terminals 21, 22, 23, and 25 in FIG. 6 isdifferent from those of FIGS. 1, 3, and 5. In other words, the terminals21, 22, 23, and 25 in FIG. 6 are bonded to a runner 26, and a lead frame20 is integrally formed. In other words, the respective terminals areheld in an integrated state as the lead frame 20 in a manufacturingprocess of the power module 901. Finally, the respective terminals 21,22, 23, and 25 are independently separated by cutting out the runner 26so as to complete the power module 901.

In FIG. 6, the IGBT chip 100 and the diode chip 110 are disposed inparallel, and each bonded to the collector circuit portion 203 of theceramic substrate 13 on the collector electrode side through the metalbonding portion 803. In addition, the IGBT chip 100 and the diode chip110 are bonded to the emitter circuit portion 202 of the ceramicsubstrate 12 on the emitter electrode side sequentially through themetal bonding portion 802, the conductor block 202A, and the metalbonding portion 801. As described above, since the emitter circuitportion 202 and the ceramic insulating layer 302 both are formed in therectangular plate shape, these ends (an end 202 b of the emitter circuitportion and an end 302 b of the ceramic insulating layer) in the exposedsurface (the exposed surface of the lead frame 20) of the respectiveterminals come to have a straight shape together. Further, the ceramicinsulating layer 302 among the components of the ceramic substrate 12 onthe emitter electrode side protrudes to the outermost side in theexposed surface of the respective terminals. Therefore, the end 302 b ofthe ceramic insulating layer also becomes an end 12 b of the ceramicsubstrate 12.

Returning to FIG. 5, a voltage Vec between the emitter electrode 102 andthe collector electrode 103 reaches a considerably high value (forexample, 1.2 kV). A voltage Veg between the emitter electrode 102 andthe gate electrode 101 is a value low by about several voltages.Therefore, a voltage Vgc between the gate electrode 101 and thecollector electrode 103 becomes almost the same value (for example, 1.2kV) as the voltage Vec.

In FIG. 5, the metal bonding portion 803 is closest to the metal wire212 among the members having a collector potential. In particular, thehighest point 803 a of the rising portion of the peripheral edge isclosest to the metal wire 212. Since the sealing portion 11 of the powermodule 901 is made of resin, there is a need to secure an insulationdistance not to cause a dielectric breakdown between the metal bondingportion 803 (specifically the highest point 803 a) and the metal wire212 according to a dielectric property of the resin and the voltage Vgc.The insulation distance is adjusted by the height of the conductor block202A. Hereinafter, the configurations of the respective portions in FIG.5 will be described in more detail.

<Metal Wire 212>

In FIG. 5, the gate electrode 101 of the IGBT chip 100 is bonded to thegate terminal 21 through the metal wire 212. The metal wire 212 hasmovability in the vertical direction of the power module 901 in a statebefore the sealing portion 11 is formed. The metal wire 212 may be madeof copper, aluminum, or gold. The cross section of the metal wire 212 isnot limited to a circular shape, but may be an elliptical shape or arectangular shape. In addition, the thickness of the metal wire in adirection of diameter or short-side may fall within a range of 10 μm to300 μm.

The metal wire 212 steeply rises to form an angle θ1 from the gateelectrode 101, approaches close to the emitter circuit portion 202 inthe vicinity of the end of the IGBT chip 100, forms a smooth loop, andis connected to the gate terminal 21. A connection point 21 a betweenthe gate terminal 21 and the metal wire 212 is located on the upperportion from the gate electrode 101 of the IGBT chip 100, and on thelower portion from the emitter circuit portion 202. Then, the angle θ1formed between the metal wire 212 and the IGBT chip 100 is larger thanan angle θ2 formed between the metal wire 212 and the gate terminal 21.

Making an explanation on the shape of the metal wire 212 in more detail,the angle θ1 rises from the gate electrode 101 toward the heat radiatingsurface 42, and the angle formed with respect to the heat radiatingsurface 42 is slightly reduced as it goes near to the ceramic substrate12 on the emitter electrode side. Then, there is a peak in which thecurvature is maximized at a position 212 b. Thereafter, the metal wire212 approaches the gate terminal 21 while keeping almost parallel withthe heat radiating surface 42, is bent to have the peak (extreme value)of the curvature again at a position 212 c in the vicinity of theconnection point 21 a, and is connected to the gate terminal 21 to formthe angle θ2 in the connection point 21 a.

Herein, the metal wire 212 has a length exceeding “L₁+√{square root over((L₂ ²+L₃ ²))}”, where L₁ is a distance between the ceramic substrate 12on the emitter electrode side and the gate electrode 101 in a directionperpendicular to the heat radiating surface 42, L₂ is a distance betweenthe ceramic substrate 12 and the connection point 21 a in the samedirection, and L₃ is a distance between the gate electrode 101 and theconnection point 21 a in a direction parallel to the heat radiatingsurface 42. Specifically, the metal wire is lengthened by 2% or morewith respect to “L₁+√{square root over ((L₂ ²+L₃ ²))}”. Further, aninterval between the metal wire 212 and the emitter circuit portion 202becomes 100 μm or less in a place where both are closest to each other.A voltage between the metal wire 212 and the emitter circuit portion 202is a value equal to the voltage Veg between the emitter electrode 102and the gate electrode 101, or lower by about several voltages.Therefore, even when the interval of the two is equal to or less than100 μm, it is possible to secure a sufficient insulation distance.Herein, the length of the metal wire 212 is determined by the shape ofthe metal wire 212, and a positional relation of the peripheral membersof the metal wire such as the emitter circuit 202, the collector circuit203, the conductor block 202A, and the gate electrode 101.

<Conductor Block 202A>

The conductor block 202A serves as a spacer to secure the insulationdistance between the emitter circuit portion 202 and the collectorcircuit portion 203. The insulation distance is determined by a maximumvoltage between two circuit portions 202 and 203 and an insulationproperty of the sealing portion 11. Since the potential of the metalwire 212 is close to the potential of the emitter circuit portion 202,the metal wire 212 is disposed close to the emitter circuit portion 202as illustrated in FIG. 5, so that the conductor block 202A also has afunction to secure the insulation distance between the metal wire 212and the collector circuit portion 203.

In addition, the heat generated in the IGBT chip 100 is radiated to theoutside through a path where the heat is transferred from the ceramicsubstrate 13 on the collector electrode side, and a path where the heatis transferred from the ceramic substrate 12 on the emitter electrodeside. With this configuration, the IGBT chip 100 can be cooled down fromboth the heat radiating surfaces 42 and 43, and a cooling efficiency canbe increased. Therefore, the conductor block 202A also has a function asa path through which the heat is transferred from the IGBT chip 100 tothe ceramic substrate 12 on the emitter electrode side. Therefore, theconductor block 202A is configured not to have a gap.

The conductor block 202A is provided to have a width and a depth largerthan the thickness (the length in the vertical direction of FIG. 5) tosustain itself at the time of the bonding process. Further, thethickness of the conductor block 202A is larger than a total thicknessof the metal bonding portions 801 and 802 in order to make theinclination and the thickness less vary at the time of bonding.Furthermore, the width and the depth of the surface facing the emitterelectrode 102 of the conductor block 202A are made smaller than those ofthe emitter electrode 102 in order to improve assembly performance.

In the conductor block 202A, copper, aluminum, molybdenum, tungsten,carbon having a high thermal conductivity, an alloy of these materials,or a composite is desirably selected in order to reduce electricresistance and thermal resistance. In addition, these materials may becombined, or an intermediate layer which has a low heat expansion ratewith respect to copper and aluminum may be provided. Further, in thisembodiment, the intermediate layer may be omitted.

<Ceramic Substrates 12 and 13>

The ceramic insulating layers 302 and 303 of the ceramic substrates 12and 13 may be made using aluminum nitride, silicon nitride, and aluminahaving a high dielectric breakdown voltage may. In particular, aluminumnitride and silicon nitride having a high thermal conductivity aredesirable. The thicknesses of the ceramic insulating layers 302 and 303are desirably set within a range of 0.1 to 1.5 mm in correspondence withthe insulation property necessary for the power module. In addition, thethicknesses of the ceramic insulating layers 302 and 303 are desirablyset to be equal in front and rear surfaces in order to reducedeformation caused by thermal stress of the power module. In addition,the ceramic insulating layer may be formed in a matrix shape usingresin, and may be formed in a sheet shape where a filler having a highthermal conductivity such as alumina, boron nitride, yttria, andaluminum nitride is mixed. However, in a case where the resin is used,there is a need to perform a mounting process after bonding the metalbonding portions 801 to 803 from the viewpoint of heat resistance.

In addition, the emitter circuit portion 202 and the collector circuitportion 203 are bonded to the emitter electrode 102 and the collectorelectrode 103 which are main electrodes of the IGBT chip 100. Therefore,it is desirable that copper, aluminum, or an alloy of these materialshaving a low electric resistance be used. In addition, since the ceramicinsulating layers 302 and 303 have expansion coefficients lower thanthose of the two circuit portions 202 and 203, an intermediate layermade of molybdenum, tungsten, and carbon having a low thermal expansionand a high thermal conductivity, or a composite of these materials andcopper or aluminum may be provided between the two circuit portions 202and 203 and the ceramic insulating layers 302 and 303. Further, in thisembodiment, the intermediate layer may be omitted. The thicknesses ofthe emitter circuit portion 202 and the collector circuit portion 203are desirably set within a range of 0.2 to 2.0 mm in correspondence withthe necessary current capacitance.

In the heat radiating portions 402 and 403, it is desirable that copper,aluminum, or an alloy of these materials having a high thermalconductivity be used. In addition, similarly to the above circuitportions 202 and 203, an intermediate layer made of molybdenum,tungsten, and carbon having a low thermal expansion and a high thermalconductivity, or a composite of these materials and copper or aluminummay be provided between the heat radiating portions 402 and 403 and theceramic insulating layers 302 and 303. In this embodiment, theintermediate layer may be omitted.

The circuit portions 202 and 203 and the heat radiating portions 402 and403 are bonded using, for example, a brazing material which can makestrong bonding to the ceramic insulating layers 302 and 303. At thistime, it is desirable that thermal stress obtained from a difference inthermal expansion rate and a Young's modulus of the circuit portions 202and 203 and the heat radiating portions 402 and 403 be set to be equalby interposing the ceramic insulating layers 302 and 303. For example,when a material having the same composition is applied to the circuitportions 202 and 203 and the heat radiating portions 402 and 403, theshape may be set to have the substantially equal volume. In addition, itis desirable that a creeping distance with respect to the ceramicinsulating layers 302 and 303 of the sealing portion 11 be set to belong by reducing one or both of the widths of the circuit portions 202and 203 and the heat radiating portions 402 and 403 with respect to thewidth of the ceramic insulating layers 302 and 303. The circuit portions202 and 203 may be manufactured to have a circuit pattern by etchingafter bonding the ceramic insulating layers 302 and 303, or the circuitpattern may be manufactured by punching before bonding.

<Sealing portion 11>

In the sealing portion 11, for example, there may be used a resin basedon epoxy resin system, acrylic system, silicone system,bismaleimide-triazine system, cyanate ester system of novolac,polyfunctional, biphenyl, and phenol types having adhesiveness. In theseresins, ceramic such as SiO₂, Al₂O₃, AlN, and BN and fillers such as geland rubber are contained, and a thermal expansion coefficient is set tobe close to those of the IGBT chip 100, the diode chip 110, and thecircuit portions 202 and 203 to reduce a difference in the thermalexpansion coefficient. With the use of these resins, the thermal stressto be generated as the temperature rises at the time of usageenvironment is significantly reduced. Therefore, it is possible toextend the life span of the power module. In a case where a materialhaving a low heat expansion is used in the circuit portions 202 and 203,and a low thermal stress is achieved, silicone gel may also be used.

Before the sealing portion 11 is sealed using the above resin, therespective circuits, the terminals, the ceramic insulating layer, theheat radiating portion, the semiconductor chip, and the metal bondingportion are desirably subjected to a process of improving an adhesivestrength with respect to the sealing portion 11. For example, a methodof forming a coating film such as polyamide imide and polyimide may beemployed.

<Metal Bonding Portions 801 to 803>

For example, a solder material, metal fine particles, or alow-temperature sintered bonding material mainly formed by metal oxideparticles may be used in the metal bonding portions 801 to 803 which areused to bond the emitter electrode 102 and the collector electrode 103.In the solder material, a solder material mainly formed by tin, bismuth,zinc, and gold having a melting point higher than a curing temperatureof the sealing portion 11 may be used. In the metal oxide particles,metal oxide which is reducible at a low temperature equal to that of thesolder material such as AgO, Ag₂O, and CuO may be applied. In a casewhere AgO, Ag₂O, and CuO are used, the metal bonding portions 801 to 803becomes a sintered silver layer or a sintered copper layer.

[Manufacturing Process]

Next, a manufacturing process of the power module 901 will be describedwith reference to FIGS. 7 to 9. First, as illustrated in FIG. 7(a), theIGBT chip 100 and the diode chip 110 (see FIG. 6) are bonded to theceramic substrate 13 on the collector electrode side through the metalbonding portion 803. In addition, the collector terminal 23 (see FIG. 6)is bonded to the collector circuit portion 203. At this time, asillustrated in FIG. 6, the collector terminal 23 is integrally formed asthe lead frame 20 through the runner 26 together with other terminals.

A positional relation between the lead frame 20 and the ceramicsubstrate 13 on the collector electrode side is determined by bondingthe collector terminal 23 to the collector circuit portion 203, and theposition of the lead frame 20 is disposed slightly upward from theoriginal position. The position of the lead frame 20 is illustrated inFIG. 7 (a) by the position of the gate terminal 21 which is a part ofthe lead frame. In FIG. 7(a), the position indicated by a broken line Bis the original position of the gate terminal 21, and the gate terminal21 is disposed slightly upward from the position.

Next, as illustrated in FIG. 7 (b), the gate electrode 101 and the gateterminal 21 are connected by the metal wire 212. The procedure is thesame as a normal wire/bonding procedure. However, a loop shape of themetal wire 212 is set to interfere in the mounting position of theceramic substrate 12 on the emitter electrode side illustrated by thebroken line. Further, the wiring of the metal wire 212 is performedbefore the ceramic substrate 12 on the emitter electrode side is bondedto the IGBT chip 100. This is because the ceramic substrate 12 on theemitter electrode side covers the gate electrode 101 when the ceramicsubstrate 12 is bonded to the IGBT chip 100, and thus the wire/bondingprocedure is not possible.

Next, as illustrated in FIG. 7(c), the conductor block 202A is bonded tothe emitter electrode 102 through the metal bonding portion 802.Further, the ceramic substrate 12 on the emitter electrode side isbonded to the conductor block 202A through the metal bonding portion801. At this time, the metal wire 212 is pressured and deformed downwardwhile abutting on the substrate 12. The emitter terminal 22 is bonded tothe ceramic substrate 12 on the emitter electrode side.

Next, as illustrated in FIG. 8(a), the power module 901 is set in molds150 and 160 for transfer molding. In FIG. 8(a), an insertion hole 162 asa groove for inserting the terminal contained in the lead frame 20 suchas the gate terminal 21 is formed in the left end of the mold 160.Further, the gate terminal 21 is inserted in the insertion hole 162illustrated in FIG. 8(a). Then, the gate terminal 21 and other terminals(not illustrated) are pressed downward by the mold 150. Herein, theposition where the insertion hole 162 is formed corresponds to theposition where each terminal is finally disposed. Therefore, the gateterminal 21 disposed at the previous position (indicated by a brokenline C on the drawing) is pressed down by the mold 150, and disposed ata position illustrated in FIG. 8(a). The other terminals are alsodisposed in parallel to the gate terminal 21 by pressing down by themold 150.

Since the metal wire 212 is formed of a material having a highplasticity, the connection point 21 a faces downward while keeping astate deformed due to the contact with the ceramic substrate 12.Therefore, the deformation is made such that the layout position of themetal wire 212 is lowered down overall. In addition, an injection hole164 as a groove for injecting a resin 11 a at the time of transfermolding is formed in the right end of the mold 160, and a pressingportion 152 is provided in the mold 150 to press the resin 11 a. Theresin 11 a is filled between the mold 150 and the mold 160 through thepressing portion 152 and the injection hole 164. When the resin 11 a isthermally cured, the sealing portion 11 is formed.

When the molds 150 and 160 are removed through the process as describedabove, the external appearance is as illustrated in FIG. 8(b). Inaddition, the plan view is as illustrated in FIG. 9. When the runner 26is cut from the lead frame 20 in FIG. 9, the terminals 21, 22, 23, and25 become separate terminals, and the power module 901 illustrated inFIG. 1 is completed.

Comparative Example

Next, the configuration according to a comparative example will bedescribed with reference to FIG. 10 in order to make the effect of thisembodiment clear. In this comparative example, a metal wire 217 isapplied in place of the metal wire 212. Since the metal wire 217 isbonded not to interfere in the layout place of the ceramic substrate 12on the emitter electrode side from the beginning, the metal wire doesnot come into contact with the ceramic substrate 12 in the manufacturingprocess. In addition, the lead frame 20 containing the gate terminal 21is determined to be disposed at the final position (see the drawing)from the beginning.

The loop shape of the metal wire 217 is a substantially triangularshape. The loop shape is determined by a route drawn by a bonding head(not illustrated) at the time of bonding. In other words, the bondinghead discharges the metal wire 217 while drawing a route such as “<”with respect to the metal wire 217, so that the loop shape such as asubstantially triangular shape is realized. Since inconvenience iscaused when the loop shape is determined by such a method, it isdifficult to accurately set the loop shape to a desired shape. Thelength which can be realized while the metal wire 217 does not interferein the ceramic substrate 12 on the emitter electrode side is notpossible to be made equal to or more than a total length of the linesegments D1 and D2 on the drawing (that is, L₁+√{square root over ((L₂²+L₃ ²)))}.

In addition, since there is a variation in the Young's modulus and theplasticity of the metal wire 217, the dimension and the shape of themetal wire 217 come to vary even when the bonding head is drawn on thesame route. There is a need to set a sufficient margin with respect tothe distance L₁ of the drawing in order for the metal wire 217 havingvariation in dimension and shape to satisfy two conditions, “Nointerference in the layout position of the ceramic substrate 12 on theemitter electrode side”, and “Sufficient insulation distance withrespect to the metal boding portion 803”. In other words, in thiscomparative example, the conductor block 202A has to be lengthened inorder to secure the distance L₁, and the power module is increased insize as much as the lengthened block compared to the embodiment.

Effect of Embodiment

As described above, the power module 901 of this embodiment includes

a first substrate (12),

a second substrate (13) which is disposed to face the first substrate(12),

a first conductive portion (202) which is provided on a side facing thesecond substrate (13) in the first substrate (12),

a second conductive portion (203) which is provided on a side facing thefirst substrate (12) in the second substrate (13),

a first terminal (22) which is bonded to the first conductive portion(202), and disposed between the first substrate (12) and the secondsubstrate (13),

a second terminal (23) which is bonded to the second conductive portion(203) and disposed between the first substrate (12) and the secondsubstrate (13),

a control terminal (21) which is disposed between the first substrate(12) and the second substrate (13),

a semiconductor chip (100) which includes a first electrode (102) and acontrol electrode (101) in one surface, and a second electrode (103) ina surface opposite to the surface,

a metal wire (212) which is drawn in an arc to connect the controlterminal (21) and the control electrode (101), and a conductor block(202A) which is disposed between the first conductive portion (202) andthe second conductive portion (203).

The semiconductor chip (100) is configured such that the first electrode(102) is connected to the first conductive portion (202) of the firstsubstrate (12) through the conductor block (202A), and the secondelectrode (103) is connected to the second conductive portion (203) ofthe second substrate (13). The metal wire (212) rises to form a firstangle (θ1) from the control electrode (101) toward the first conductiveportion (202), gradually goes in substantially parallel to the firstconductive portion (202) as it approaches the first conductive portion(202), and is connected to the control terminal (21) to form a secondangle (θ2) smaller than the first angle (θ1).

In addition, the metal wire (212) has a length exceeding “L₁+√{squareroot over ((L₂ ²+L₃ ²))}”, where L₁ is a distance between the firstsubstrate (12) and the control electrode (101) in a directionperpendicular to the first conductive portion (202), L₂ is a distancebetween the first substrate (12) and the connection point (21 a) of themetal wire (212) in the control terminal (21) in a directionperpendicular to the first conductive portion (202), and L₃ is adistance between the control electrode (101) and the connection point(21 a) in a direction in parallel to the first conductive portion (202).With the configuration described above, this embodiment obtains thefollowing effects.

(1) According to this embodiment, the shape and the length of the metalwire 212 are set as described above, so that it is possible to form thepower module 901 to be thin (small) while securing a sufficientinsulation distance between the metal wire 212 and the member (such asthe metal bonding portion 803) to be at the collector potential.

(2) Further, in the manufacturing process illustrated in FIGS. 7 to 9,the ceramic substrate 12 comes into contact with the metal wire 212, andthe metal wire 212 is deformed when the ceramic substrate 12 on theemitter electrode side is bonded after the metal wire 212 is connected(see FIG. 7 (c)). With this configuration, there is no need to considera variation in loop height of the metal wire 212, and a margin to thethickness of the conductor block 202A can be reduced, so that the powermodule 901 can be made thinner.

The metal wire 212 coming into contact with the emitter circuit portion202 moves downward using the movability of the gate terminal 21 in theprocess of FIG. 8(a) (setting to the molds 150 and 160), so that aslight gap can be formed between the emitter circuit portion 202 and themetal wire 212. Since a potential difference between the metal wire 212and the emitter circuit portion 202 is about several volts at the timeof using the power module 901, it is possible to secure a sufficientinsulation distance even when a slight gap is formed.

(3) In addition, according to this embodiment, the pattern of thecollector circuit portion 203 can be effectively simplified byseparating the gate terminal 21 from the ceramic substrate 13 on thecollector electrode side. For example, the pattern of the collectorcircuit portion 203 can be simplified until the pattern has the sameshape as that of the ceramic insulating layer 303. The ceramic substrate13 on the collector electrode side includes the collector circuitportion 203 made of metal having a large thermal expansion coefficient,and the ceramic insulating layer 303 having a small thermal expansioncoefficient. Therefore, a stress may be easily focused on the end of thepattern of the collector circuit portion 203, and the ceramic insulatinglayer 303 may be easily cracked by the thermal stress caused by atemperature cycle. On the contrary, according to this embodiment, thepattern of the collector circuit portion 203 can be simplified, so thata region to cause the stress focusing becomes small. Therefore, it ispossible to improve reliability.

(4) In addition, when the pattern of the collector circuit portion 203is simplified, the shape of the ceramic insulating layer 303 itself canbe simplified. Therefore, the ceramic substrates 12 and 13 on thecollector and emitter sides can be manufactured to be substantiallyequal in structure, so that the costs can be effectively reduced throughthe commonalization.

(5) In addition, according to this embodiment, the respective terminals(the gate terminal 21, the emitter terminal 22, the collector terminal23, and the sense emitter terminal 25) are lead out from the samesurface of the power module 901 in the same direction. With such ashape, an external dimension of the power module 901 containing therespective terminals can be reduced. In addition, according to thisembodiment, the terminals 22 and 23 are lead out from places facing thediode chips 110 (see FIG. 3). Since there is no control electrode (thegate electrode 101 of the IGBT chip 100) in the diode chip 110, thewidth between the terminals 22 and 23 can be secured wide, and thecapacity of the power module 901 can be increased. In addition, thedistance between the emitter terminal 22 and the collector terminal 23can be also secured wide, and a high breakdown voltage of the powermodule 901 can be achieved.

[Modification]

The invention is not limited to the above embodiments, and variousmodifications can be made. The above embodiments are described in aclearly understandable way for the invention, and thus the invention isnot necessarily to provide all the configurations described above. Inaddition, some configurations of a certain embodiment may be replacedwith the configurations of another embodiment, and the configuration ofthe other embodiment may also be added to the configuration of a certainembodiment. Additions, omissions, and substitutions may be made on someconfigurations of each embodiment using other configurations. Thepossible modifications with respect to the embodiments are as followsfor example.

(1) A configuration of a power module according to a modification of theembodiment will be described with reference to FIGS. 10(a) to 10(c).FIG. 10(a) illustrates the power module of this modification in whichthe sealing portion is excluded. This modification is different from theembodiment (FIG. 3) in that metal wires 213 and 253 are employed inplace of the metal wires 212 and 252. As illustrated in FIG. 10(a),parts of the metal wires 213 and 253 are curved in a lateral direction(a layout direction of the terminals 21, 22, 23, and 25).

Herein, a perspective view of the metal wire 213 is illustrated in FIG.10(b). The metal wire 213 has the loop shape as indicated by a brokenline E at the time of bonding, and then curved in the lateral direction.In other words, the metal wire 213 is curved in the place near to theceramic substrate 12 on the emitter electrode side in a projection shapewith respect to the ceramic substrate 12 on the emitter electrode side.In order to realize such a curved shape, as illustrated in FIG. 10(c),the ceramic substrate 12 on the emitter electrode side may be disposedslightly inclined with respect to the layout direction of the terminals21, 22, 23, and 25 so as to press the metal wires 213 and 253.

The metal wires 213 and 253 are curved in the same direction, so thatthe contact can be prevented even when the wires are adjacent to eachother. Thereafter, the processes described in FIGS. 8(a), 8(b), and 9are performed, and the metal wires 213 and 253 are configured not tocome into contact with the ceramic substrate 12 at the time of transfermolding as described in the above embodiment. Even in this modification,the metal wires 213 and 253 can be disposed near to the ceramicsubstrate 12 while securing a sufficient insulation distance withrespect to the member (such as the metal bonding portion 803 of FIG. 5)to be at the collector potential. Therefore, the power module can beconfigured to be thin and small as described in the above embodiment.

(2) In addition, the gate electrode 101 and the gate terminal 21 areconnected by the metal wire 212 in the manufacturing process of theembodiment (FIG. 7 (b)), and then the conductor block 202A is bonded tothe emitter electrode 102 (FIG. 7(c)). However, first the conductorblock 202A is bonded to the emitter electrode 102, and then the gateelectrode 101 and the gate terminal 21 may be connected by the metalwire 212.

(3) In the above embodiment, the gate terminal 21 has been drawn fromthe same surface and the same direction as those of the emitter terminal22 and the collector terminal 23. The gate terminal 21 may be drawn froma surface different from that of the emitter terminal 22 and thecollector terminal 23. In addition, in the above embodiment, the gateterminals 21 are independently provided with respect to two IGBT chips100, or may share one terminal 21. In addition, the emitter terminal 22and the collector terminal 23 may branch into plural pieces. In thiscase, when the emitter terminal and the collector terminal arealternately arranged, inductance can be lowered.

(4) In the above embodiment, an application of the IGBT chip 100 hasbeen described as a specific example of the “semiconductor chip”.However, the “semiconductor chip” is not limited to the IGBT chip 100,and a MOSFET, a thyristor, a gate turn-off thyristor, and a triac may beused. In addition, in the above embodiment, an example of the IGBT chip100 equipped with the gate electrode 101 and the sense emitter electrode104 has been described as the control electrode. The control electrodemay be configured only by the gate electrode 101, or may be added withthe electrode of thermistor.

REFERENCE SIGNS LIST

-   11 sealing portion (housing)-   11 a resin-   12 ceramic substrate on emitter electrode side (first substrate)-   12 b end-   13 ceramic substrate on collector electrode side (second substrate)-   20 lead frame-   21 gate terminal (control terminal)-   21 a connection point-   22 emitter terminal (first terminal)-   23 collector terminal (second terminal)-   25 sense emitter terminal-   26 runner-   42, 43 heat radiating surface-   100 IGBT chip (semiconductor chip)-   101 gate electrode (control electrode)-   102 emitter electrode (first electrode)-   103 collector electrode (second electrode)-   104 sense emitter electrode-   110 diode chip-   150, 160 mold-   152 pressing portion-   162 insertion hole-   164 injection hole-   202 emitter circuit portion (first conductive portion)-   202A conductor block-   203 collector circuit portion (second conductive portion)-   212, 213, 252, 253 metal wire-   302, 303 ceramic insulating layer-   402, 403 heat radiating portion-   801 to 803 metal bonding portion-   901 power module

1. A semiconductor module, comprising: a first substrate; a secondsubstrate that is disposed to face the first substrate; a firstconductive portion that is provided on a side facing the secondsubstrate in the first substrate; a second conductive portion that isprovided on a side facing the first substrate in the second substrate; afirst terminal that is bonded to the first conductive portion, anddisposed between the first substrate and the second substrate; a secondterminal that is bonded to the second conductive portion, and disposedbetween the first substrate and the second substrate; a control terminalthat is disposed between the first substrate and the second substrate; asemiconductor chip that includes a first electrode and a controlelectrode in one surface, and a second electrode in a surface oppositeto the surface; a metal wire that is drawn in an arc to connect thecontrol terminal and the control electrode; and a conductor block thatis disposed between the first conductive portion and the secondconductive portion, wherein the semiconductor chip is configured suchthat the first electrode is connected to the first conductive portion ofthe first substrate through the conductor block, and the secondelectrode is connected to the second conductive portion of the secondsubstrate, wherein the metal wire rises to form a first angle from thecontrol electrode toward the first conductive portion, gradually goes insubstantially parallel to the first conductive portion as the metal wireapproaches the first conductive portion, and is connected to the controlterminal to form a second angle smaller than the first angle, whereinthe metal wire has a length exceeding “L₁+√{square root over ((L₂ ²+L₃²))}” where, L₁ is a distance between the first substrate and thecontrol electrode in a direction perpendicular to the first conductiveportion, L₂ is a distance between the first substrate and a connectionpoint of the metal wire in the control terminal in a directionperpendicular to the first conductive portion, and L₃ is a distancebetween the control electrode and the connection point in a direction inparallel to the first conductive portion, and wherein the metal wire hasa place near to the first substrate with a distance equal to or lessthan 100 μm.
 2. (canceled)
 3. (canceled)
 4. The semiconductor moduleaccording to claim 1, wherein the first substrate and the secondsubstrate have the same shape and the same size.
 5. The semiconductormodule according to claim 1, wherein an end of the first conductiveportion is formed in a straight shape in a surface where the controlterminal is exposed from between the first substrate and the secondsubstrate.
 6. The semiconductor module according to claim 1, wherein anend of the first substrate is formed in a straight shape in a surfacewhere the control terminal is exposed from between the first substrateand the second substrate.
 7. The semiconductor module according to claim1, wherein a shape of the metal wire projected to the first substrate iscurved in a place near to the first conductive portion.
 8. A method ofmanufacturing a semiconductor module that includes a first substrate, asecond substrate that is disposed to face the first substrate, a firstconductive portion that is provided on a side facing the secondsubstrate in the first substrate, a second conductive portion that isprovided on a side facing the first substrate in the second substrate, afirst terminal that is bonded to the first conductive portion, anddisposed between the first substrate and the second substrate, a secondterminal that is bonded to the second conductive portion, and disposedbetween the first substrate and the second substrate, a control terminalthat is disposed between the first substrate and the second substrate, asemiconductor chip that includes a first electrode and a controlelectrode in one surface, and a second electrode in a surface oppositeto the surface, a metal wire that is drawn in an arc to connect thecontrol terminal and the control electrode, and a conductor block thatis disposed between the first conductive portion and the secondconductive portion, the method comprising: bonding the second electrodeto the second conductive portion of the second substrate; bonding theconductor block to the first electrode of the semiconductor chip, andconnecting the metal wire such that the control electrode and a bondingplace of the control terminal by the metal wire interfere in a layoutplace of the first substrate; bonding the first substrate to theconductor block while pressing the metal wire by the first substrate;moving a position of the control terminal in a direction away from thefirst substrate to separate the metal wire from the first substrate; andsealing a space between the first substrate and the second substrate bya transfer mold.